For hundreds of years and more, hogs were allowed to roam freely in the woods or were penned in fenced pastures. This use of open space allowed the random placement of swine fecal waste and urine to be spread over a rather large area. There was not, usually, a heavy enough build up of waste in one area to cause anything other than a short term, often minor problem. The last few decades, however, have witnessed a radical change in the method of producing swine for market. The modern swine farm utilizes long confinement houses containing several hundred hogs at one time.
In a typical facility, the animals are grown on slotted concrete floors called “slats”. Therein, an upper floor is raised above a concrete subfloor that receives the waste from the animals through the slots in the upper floor. The lower floor accumulates the swine fecal and urinary waste until such time as the waste is flushed by wastewater from a flushing tank. The flushing cycle can vary from a few hours to as much as a week depending upon the type of flushing system.
Other swine facilities use a solid, sloped floor having a gutter along the outside wall. With such a system, the pigs have direct access to the gutter and the flush water. The flush water in both of the above facilities is pumped from the top of a waste holding lagoon. When the pigs confined in a gutter type facility hear the flush water being released, they will run into the gutter, often lie in it and proceed to drink the flush water and eat the fecal matter in it. So many pigs will stand or lie in the gutter that it interferes with the adequate cleaning of the gutter.
The houses are flushed by several hundred gallons of water released from the flush holding tanks supplied from the lagoon. The flushed waste water is recycled, without treatment, to the waste holding lagoon.
The flush holding tanks located at the end of the houses opposite the lagoon are refilled from the top area of the lagoon to be ready for the next flush cycle. The lagoon is a man-made pond for collecting and storing the waste from the confinement houses and from which, after partial settling of the solids, wastewater is obtained for the next flushing cycle. Resultantly, modern swine production and the attendant holding lagoons generate substantial odors and present dangers of ground, ground water, and stream pollution. Other adverse results include lowered property values for adjacent properties and ground water depletion.
To get rid of excess water from the lagoon, the producer must pump the wastewater onto fields that have enough area to absorb and retain the effluent. This is especially critical during periods of heavy rainfall, such as that associated with a tropical storm or hurricane. Accordingly, the farmer must purchase and maintain an expensive irrigation system, fence and maintain a pasture, buy or build a small herd of cattle, purchase hay rakes, balers, and mowers just to service the lagoon.